All things you need to do when designing a database fills books. In fact, if you're just getting started at database design, I'd strongly recommend reading a bunch of books. It's way too easy to get this stuff wrong. I'd start with Louis Davidson. I love the way he teaches.
"The credit belongs to the man who is actually in the arena, whose face is marred by dust and sweat and blood"
- Theodore Roosevelt
Author of:
SQL Server Execution Plans
SQL Server Query Performance Tuning